JPS59398A - Freeze-thawing type dehydrator for sludge - Google Patents

Abstract

PURPOSE:To obtain the titled dehydrator which can perform the efficient dehydration of sludge, while contriving to shorten a time required for the freeze-thawing of sludge by rapidly thawing frozen sludge, by adopting the constitution that the thawing of frozen sludge in a freeze-thawing tank is performed with heat formed by an applied electric current. CONSTITUTION:When conc. sludge in a tank 1 for freeze-thawing sludge is freezed, an electric current is applied from an AC power source 14 to each heat-transmitting plate 2. An electric current is then applied between the heat-transmitting plates 2b and 2a, 2c, 2d and 2c, 2c, etc. through the sludge containing large amounts of electrolytes such as Cl<-> and SO4<2-> in its components. Hence, the thawing of the freezed sludge is performed with heat formed by the applied electric currents. By this freeze-thawing sludge dehydrator, the thawing speed of the freezed sludge can be desirably adjusted by controlling the applied electric currents. In addition, the surfaces of the heat-transmitting plates 2 can be held at a low temp. by holding cold brine standing in the heat-transmitting plates 2 during the application of an electric current, so that the corrosion of the heat-transmitting plates 2 caused by the applied electric current can be inhibited. In the drawing, numerals 7, 9, 10 and 11 represent a cooler, an automatic change-over valve, a tank for reserving conc. sludge and a pump for applying an electric current, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a freeze-thaw type sludge dewatering treatment apparatus for cylindrical organic sludge with a water injection rate generated in sewage treatment, human waste treatment, etc.

The above-mentioned organic sludge is highly hydrophilic and colloidal, so it is extremely difficult to dehydrate it as it is. However, it is known that when such sludge is subjected to freeze-thaw treatment, aggregation of colloids is promoted and dewaterability of the sludge is improved.

Figures 1 and 2 show a vertical cross-sectional view and a plan view of a freeze-thaw tank in a freeze-thaw sludge dewatering equipment. A plurality of heat transfer plates forming a heat exchanger for heating are incorporated. The freeze-thaw tank is usually a steel tank, and the inner surface in contact with the sludge is coated with an anti-corrosion lining 3 made of rubber or epoxy paint to protect the tank from corrosion caused by the sludge. Further, each of the heat exchanger plates λ is held in an electrically independent state in the freeze-thaw tank by a stopper made of insulating rubber attached to the inner wall of the freeze-thaw tank. A heat transfer plate is usually made by stacking thin metal plates and performing seam welding to form a pline passage inside, and is connected to a pline header 6 by a pressure-resistant rubber hose 5. There is.

FIG. 3 is a flow sheet diagram showing the structure of a freeze-thaw section of a conventional freeze-thaw type sludge dewatering treatment apparatus having the freeze-thaw tank. In the figure, l and 6 are
The melter and pline header are the same as in the figure. 7 and g are a pline cooler and a pline heater, and these plines are connected to the pline header 6 via an automatic pline switching valve 9. I
O is a thickened sludge storage tank, // is a sludge feed pump, /2 is a pulp that adjusts the sludge feed, and /3 is a freeze-thaw sludge tank.

In the freeze-thaw type sludge treatment apparatus described above, the freeze-thaw tank is filled with concentrated sludge from the thickened sludge storage tank 10, which stores sludge that has been subjected to concentration treatment prior to freezing treatment, by the sludge supply pump/l, Next, cold brine is supplied from the pline cooler 7 to the heat exchanger plate/2 through the pline header 6 to freeze the sludge. When the freezing of the sludge is completed, the pline automatic switching valve operates, and this time, the brine is Warm brine is supplied from the heater g to the heat exchanger plate to melt the frozen sludge.

The above-mentioned sludge freeze-thaw treatment is performed at a cycle of 90 to 20 minutes, and the sludge frozen and thawed in freeze-thaw tank 1 is discharged to freeze-thaw sludge tank /3, and this freeze-thaw treatment cycle is repeated. Therefore, the amount of sludge treated is determined by the time required for freezing and thawing the sludge in the freeze-thaw tank, so in order to increase the amount of sludge treated per unit time,
It is necessary to shorten the freezing and thawing time of sludge, but since there is an appropriate freezing time to improve the flocculation of sludge and coarsen the sludge particles, it is necessary to simply increase the performance of the line cooler and freeze the sludge. Time cannot be shortened arbitrarily.

For this reason, in conventional freeze-thaw sludge dewatering equipment, the third
As shown in the figure, several freezing and thawing tanks are installed in parallel, and the structure is such that freezing and thawing are repeated alternately.
In this method, the freezing time and thawing time must be equal.The freezing and thawing time of sludge is determined by the freezing time, so in order to increase the amount of sludge processed per unit time, it is necessary to add a freeze-thaw tank. I have to rely on it, but
When adding a freeze-thaw tank, there are drawbacks such as the cost and space needed for the addition. In addition, the corrosion reaction rate of the heat exchanger plate in a freeze-thaw tank is greatly affected by temperature, and while it can be ignored for cold brine, it cannot be ignored for hot brine, an unresolved problem. ing. The main object of the present invention is to provide a freeze-thaw sludge dewatering device that solves the problem of corrosion of heat exchanger plates caused by hot brine by performing a freeze-thaw treatment by rapidly thawing frozen sludge. .

That is, the present invention provides a sludge freeze-thaw tank incorporating a heat exchanger constituted by a plurality of individually independent heat exchanger plates, in which mutually opposing surfaces of the heat exchanger plates serve as different electrodes. This system is characterized by a structure in which the heat transfer plates are divided into two or more groups, and by passing an alternating current between the electrodes, the frozen sludge in the freeze-thaw tank is melted by electrical heating.

Hereinafter, the present invention will be explained in detail with reference to drawings showing embodiments thereof. Figure 1 is a flow sheet diagram illustrating the structure of the freeze-thaw section of the freeze-thaw sludge dewatering equipment of the present invention, and Figure S is a diagram showing the heat transfer plate in the freeze-thaw tank and the AC power source in an embodiment of the present invention. FIG.

In the figure, /,2. t~/3 is the same as in FIGS. 1 to 3. /Hiro is an AC power supply for supplying power to the heat exchanger plate.

In the connection state shown in FIG. S, the heat exchanger plate 2a.

2 c, 2. One electrode is formed at e..., and 2
k), 2d.

The other electrode is formed at 2f... In this invention, the steps up to the freezing treatment of the sludge filled in the freeze-thaw tank are the same as those of the conventional apparatus described above. In the apparatus of this invention, when the sludge in the freeze-thaw tank freezes, power is supplied to each heat exchanger plate from the AC power source /l, as shown in FIG. S.

Sludge contains a large amount of electrolytes such as chloride ions, sulfate ions, and sodium ions in its components, so between the heat exchanger plates 2b and 2a and 20, and between the heat exchanger plates 2d and 2c. , 20, etc., through the sludge, and the frozen sludge is thawed by the heat generated by the current.

According to the freeze-thaw sludge dewatering apparatus configured as described above, the melting rate of frozen sludge can be arbitrarily adjusted by controlling the flow t″Nt. By retaining and retaining the cold prine inside, the surface of the heat exchanger plate is maintained at a low temperature, which prevents corrosion of the heat exchanger plate due to energization.As the energizing power source, either a DC power source or an AC power source can be used. However, considering the corrosion of the heat exchanger plates that serve as electrodes due to electricity, DC power supplies are unsuitable because the electrodes that serve as anodes are likely to corrode, and they are not suitable for use due to galvanic corrosion. An AC power supply with little influence is suitable.In particular, in the case of a high frequency current of /K)1z or more, there is almost no problem of 15tE galvanic corrosion.

FIG. 6 is a schematic diagram showing connection means between a heat exchanger plate in a freeze-thaw tank and an AC power source in another embodiment of the present invention, and in the figure, /, 2a to 2f.

/da is the same as in FIG.

As described above, in the freeze-thaw type sludge dewatering treatment apparatus, the frozen sludge in the freeze-thaw tank is melted by electrical heating, so that the sludge is sludged by rapid melting of the frozen sludge. It is possible to effectively improve efficiency by shortening the freeze-thaw processing time, and since there is no need to use high-temperature brine to thaw frozen sludge, there is no problem of corrosion due to warm prine, compared to conventional freeze-thaw. All defects in tanks can be eliminated.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a freeze-thaw tank in a conventional freeze-thaw sludge dewatering equipment, Figure 2 is a cross-sectional view, and Figure 3 is the configuration of the freeze-thaw section of a conventional freeze-thaw sludge dewatering equipment. FIG. 5 is a flow sheet diagram showing the configuration of the freeze-thaw section according to the present invention, and FIG. 5 is a flow sheet diagram showing the configuration of the freeze-thaw section according to the present invention. FIG. 6 is a plan view showing a connection means between a heat exchanger plate in a freeze-thaw tank and an AC power source in another embodiment. ／・・Freeze-thaw tank, ・・Heat exchange plate, 3.・Anti-corrosion treated liner, ・・Stopper, S.・Rubber hose, 6.・・Pline header, ? ...cooler, g...heater,?・・・
Automatic switching valve, 10... Thickened sludge storage tank, l/... Sludge supply pump, /2... Sludge supply amount adjustment pulp, /3... Freeze-thaw sludge tank, /l... AC power supply, 2a-λf... heat transfer plate. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Agent Shin Kuzuno −

Claims (1)

[Scope of Claims] In a sludge freeze-thaw tank incorporating a heat exchanger constituted by a plurality of individually independent heat exchanger plates, the mutually opposing surfaces of the heat exchanger plates serve as different electrodes. By heating at least two groups of heat transfer plates and passing a cross current between the electrodes,
A freeze-thaw type sludge dewatering device, characterized in that the frozen sludge in the sludge freeze-thaw tank is thawed by electrical heating.